Surface restructuring Ni0.85Se/ZnSe catalyst shows large boosting electrocatalytic and photoelectrochemical performance

Catalytic performance is often affected by electronic band structure. Here, it is demonstrated that though loading ZnSe on the surface of Ni0.85Se to build Ni0.85Se/ZnSe heterojunction catalysts. The electronic band structure of Ni0.85Se/ZnSe heterojunction can be adjusted by the loading ZnSe, which largely affects the electrocatalytic and photoelectrochemical performance. Compared with pristine Ni0.85Se (1.49 eV) and ZnSe (2.50 eV), the bandgap of Ni0.85Se/ZnSe change from 1.28 to 1.60 eV, which is even lower than that of Ni0.85Se and ZnSe. Meanwhile, the positions of the conduction and valence bands of composites also show unusual changes: NZS2 has the highest conduction band of −0.78 eV which is higher than that of Ni0.85Se (−0.62 eV) and ZnSe (−0.66 eV) while NZS3 shows the lowest valence band of 0.88 eV which is also little lower than that of Ni0.85Se (0.87 eV). The characteristics of this adjustable electronic band structure bring obvious changes in catalytic performance. In the hydrogen evolution reaction tests, NZS2 has the lowest overvoltage of 209 mV and Tafel slope of 56 mV/dec, and NZS3 shows the lowest overvoltage of 318 mV and Tafel slope of 89 mV/dec in the oxygen evolution reaction. As compared, the Ni0.85Se has an overvoltage of 247 mV and Tafel slope of 77 mV/dec in hydrogen evolution reaction, and cannot achieve current density of 10 mA/cm2 in oxygen evolution reaction. It is considered that the higher conduction band is beneficial for reduction reaction and lower valence band means higher oxidation capacity. Moreover, the loading of ZnSe enhances the carrier's separation efficiency which causes higher photoelectrochemical performance.